Forest diversity from Canada to the sub-tropics influenced by family proximity

Date:

May 17, 2012

Source:

Indiana University

Summary:

How species diversity is maintained is a fundamental question in biology. Biologists have shown for the first time that diversity is influenced on a spatial scale of unparalleled scope, in part, by how well tree seedlings survive under their own parents.

Share:

Total shares:

FULL STORY

Data from over 3 million trees in the eastern half of the US were aggregated into two-degree-latitude-by-longitude cells in order to study regional patterns of conspecific negative density dependence, a process where the mortality of a species rises in coincidence with its increasing abundance.

Credit: Indiana University

Data from over 3 million trees in the eastern half of the US were aggregated into two-degree-latitude-by-longitude cells in order to study regional patterns of conspecific negative density dependence, a process where the mortality of a species rises in coincidence with its increasing abundance.

Credit: Indiana University

How species diversity is maintained is a fundamental question in biology. In a new study, a team of Indiana University biologists has shown for the first time that diversity is influenced on a spatial scale of unparalleled scope, in part, by how well tree seedlings survive under their own parents.

Data from over 3 million trees in the eastern half of the U.S. were aggregated into two-degree-latitude-by-longitude cells in order to study regional patterns of conspecific negative density dependence, a process where the mortality of a species rises in coincidence with its increasing abundance.

Scientists have long considered conspecific negative density dependence (CNDD), a process where the mortality of a species rises in coincidence with its increasing abundance, to be a key mechanism maintaining diversity at the local scale. In new research to be published May 17 in the journal Science, the IU researchers show that this mechanism is driving diversity from the boreal forests to sub-tropical forests.

The report, "Conspecific negative density dependence and forest diversity," is authored by Daniel Johnson, a doctoral student in the IU Bloomington College of Arts and Sciences' Department of Biology. Co-authors are Wesley T. Beaulieu, also a doctoral student in the Department of Biology, and biology professors James D. Bever and Keith Clay, Johnson's major advisor.

Their work analyzed data on forest composition from over 200,000 plots containing more than 1.3 million trees and from paired plots containing over 1.7 million seedlings of 151 different tree species. The plots were located from the Canadian border south to Florida and from the Atlantic coast to the 100th meridian and covered over 1.5 million square miles. The U.S. Forest Service spends about $62 million each year to gather the publicly available forest inventory data used in the IU study.

"We are now able to provide robust evidence that CNDD is pervasive in forest communities from boreal to sub-tropical regions and that it can significantly affect the relative abundance and richness of species with and between forests," Johnson said. "And we now see that the ability to which one tree species can sustain itself in the same area has profound impacts on the diversity of species at a spatial scale that has not been attainable previously. This is the first time it's been shown to be happening not just at a local spatial scale but over the entire eastern US."

The concept of CNDD is based on the well-known Janzen-Connell hypothesis, which proposes that the close proximity of adults reduces seedling survival of that species through increased attack by host-specific pests and pathogens.

Studies of CNDD in the past have mostly focused on forest communities at single sites or of a single species, with the most recent work showing that in tree species, composition and abundance can be influenced by CNDD at the scale of individual trees.

"Local interactions have previously been considered to affect species diversity at a local scale, but our findings indicate that local interactions feed back to species richness and abundance over much larger geographical scale, spanning most of eastern North America," Johnson said.

Evidence that local interactions underlie regional species richness is in contrast to the current understanding that patterns of forest diversity are primarily driven by temperature, precipitation and other physical aspects of the environment. This discovery has implications for how forest modeling is conducted and conservation and management decisions are made.

Indiana University. "Forest diversity from Canada to the sub-tropics influenced by family proximity." ScienceDaily. ScienceDaily, 17 May 2012. <www.sciencedaily.com/releases/2012/05/120517143504.htm>.

Indiana University. (2012, May 17). Forest diversity from Canada to the sub-tropics influenced by family proximity. ScienceDaily. Retrieved August 2, 2015 from www.sciencedaily.com/releases/2012/05/120517143504.htm

Indiana University. "Forest diversity from Canada to the sub-tropics influenced by family proximity." ScienceDaily. www.sciencedaily.com/releases/2012/05/120517143504.htm (accessed August 2, 2015).

July 31, 2015  Resettlement projects in the Amazon are driving severe tropical deforestation, according to new research. Widely hailed as a socially responsible and 'innocuous' strategy of land redistribution, ... read more

July 31, 2015  The humble butterfly could hold the key to unlocking new techniques to make solar energy cheaper and more efficient, pioneering new research has shown. By mimicking the v-shaped posture adopted by ... read more

July 30, 2015  China needs to reduce its dependence on coal and improve the range of fuels it uses if it is to have long term energy security, according to new research. The study looks at the future of electricity ... read more

July 30, 2015  North of the Aleutian Islands, submarine canyons in the cold waters of the eastern Bering Sea contain a highly productive 'green belt' that is home to deep-water corals as ... read more

July 30, 2015  New findings have implications for questions regarding how animals and plants grow minerals into shapes that have no relation to their original crystal symmetry, and why some ... read more

July 30, 2015  A new study addresses an important question in climate science: how accurate are climate model projections? Climate models are used to estimate future global warming, and their accuracy can be ... read more

Sep. 30, 2014  The resistance of forests to drought has been studied, with a focus on the diversity of tree species. This study shows that mixed species forests are more resistant to drought stress than ... read more

Apr. 22, 2013  Several hypotheses have been proposed to explain the higher species numbers in the tropics, but these hypotheses have never been tested for the ants, which are one of the most ecologically and ... read more

Sep. 25, 2012  Researchers have demonstrated for the first time that a high level of species diversity in alpine plants does not necessarily go hand in hand with a high level of genetic diversity. This finding ... read more

Nov. 22, 2010  Biologists have long thought that interactions between plants and pollinating insects hasten evolutionary changes and promote biological diversity. However, new findings show that some interactions ... read more